1. Field of the Invention
The present invention relates to a full-resonant power circuit device for receiving a variable input voltage, and more particularly, the full-resonant power circuit device switches to vary a resonance inductor for providing a stable voltage to a load in response to the variable input voltage.
2. Description of the Prior Art
Reference is made from FIG. 1, which is a schematic view of a half-bridge full-resonant converter of the prior art. In the present day, a structure of a full-resonant converter is based on a half-bridge topology or a full-bridge topology. A switch Q1 and a switch Q2 are connected to be a half-bridge structure and are switched by a variable switching frequency controlling method. When a switching frequency between the switch Q1 and switch Q2 is higher than a resonance frequency obtained from a resonance capacitor Cr and a resonance inductor Lr, the switch Q1 and the switch Q2 are conducted at a zero voltage for reducing the consumption of the switch Q1 and the switch Q2 therebetween. Moreover, the half-bridge full-resonant power circuit adjusts the switching frequency between the switch Q1 and the switch Q2 or the resonance frequency obtained from the resonance capacitor Cr and the resonance inductor Lr for adjusting a magnitude of an output voltage Vo.
However, no matter the half-bridge or the full-bridge full-resonant converter, for obtaining the stabilization of the output voltage Vo, the value of the resonance inductor Lr should be designed in response to a variational input voltage AC. Hence, the range of the variational input voltage AC can't too large for the half-bridge or the full-bridge full-resonant converter.
Reference is made from FIG. 2, which is schematic view of the half-bridge full-resonant converter with a power factor corrector (PFC) of the prior art. The half-bridge full-resonant converter is often applied to supply a high power, and due to the high power of the full-resonant converter, the power factor of the full-resonant converter is relatively low. Therefore, it is often to use a power factor corrector 2 to improve the power factor so as to conform to the IEC61000-3-2 standards. And the power factor corrector 2 not only improves the power factor but provides a stable voltage to the full-resonant converter so as to stabilize the output voltage Vo thereof. However, the power factor corrector 2 boosts variational input voltage AC into a supply voltage Vin for being used by the full-resonant converter, the power factor corrector 2 will produce a high current in the conversion condition to increase the consumption of a switch transistor QPFC of the power factor corrector 2 so as to reduce the efficiency of the power circuit device.
The inventor of the present invention recognizes the above shortage should be corrected and special effort has been paid to research this field. The present invention is presented with reasonable design and good effect to resolve the above problems.